Individualized Correction Factors in the Preselection of Hearing Aids This study investigated three issues involving corrections for individual ear acoustics in hearing aid prescriptions: (a) the extent to which inconsistencies in the sound-field reference position can affect comparative corrections for the real-ear unaided response (REUR); (b) the extent to which individual variability in the real-ear-to-coupler level difference (RECD) supports ... Research Article
Research Article  |   April 01, 1992
Individualized Correction Factors in the Preselection of Hearing Aids
 
Author Affiliations & Notes
  • Selda Fikret-Pasa
    Northwestern University Evanston, IL
  • Lawrence J. Revit
    Frye Electronics, Inc. Tigard, OR
Article Information
Hearing Disorders / Hearing Aids, Cochlear Implants & Assistive Technology / Hearing / Research Articles
Research Article   |   April 01, 1992
Individualized Correction Factors in the Preselection of Hearing Aids
Journal of Speech, Language, and Hearing Research, April 1992, Vol. 35, 384-400. doi:10.1044/jshr.3502.384
History: Received January 11, 1991 , Accepted June 11, 1991
 
Journal of Speech, Language, and Hearing Research, April 1992, Vol. 35, 384-400. doi:10.1044/jshr.3502.384
History: Received January 11, 1991; Accepted June 11, 1991

This study investigated three issues involving corrections for individual ear acoustics in hearing aid prescriptions: (a) the extent to which inconsistencies in the sound-field reference position can affect comparative corrections for the real-ear unaided response (REUR); (b) the extent to which individual variability in the real-ear-to-coupler level difference (RECD) supports the use of individual measurements as opposed to an average-ear estimate; and (c) the adequacy of using KEMAR estimates of the effects of the location of the hearing aid microphone. In Experiment 1, KEMAR REURs using over-the-ear and under-the-ear reference positions were compared with KEMAR REURs using a center-of-head reference position. Maximum differences of 4–9 dB were found in the 1500- to 5000-Hz range, depending on test conditions. In Experiment 2, the ear canal response of an insert earphone was compared to the 2-cc coupler response of the same earphone to calculate the RECD. Individual RECDs for a population of hearing aid candidates were compared to the RECD for KEMAR. For 8 of the 15 subjects (9 of 18 ears), the RECD was more than 4 dB different from KEMAR at two or more third-octave frequencies between 500 and 4000 Hz. In Experiment 3, the effect of the location of the hearing aid microphone for in-the-ear (ITE) and in-the-canal (ITC) locations was compared with the over-the-ear (OTE) location for 18 ears and for KEMAR. The effects varied across individual ears, but all ears and KEMAR showed positive gain in the high frequencies for the ITE and ITC locations. The relevance of these results to hearing aid prescription practices is discussed.

Acknowledgments
The authors wish to thank Mead C. Killion for his invaluable assistance throughout this study. We also wish to thank David B. Hawkins and Richard C. Seewald for their informative reviews of an earlier version of this manuscript.
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